Thread tensioning device for sewing machines

ABSTRACT

A sewing machine has an upper arm containing upper thread tensioning means within the arm so as to be substantially concealed from view. The arm has two thread guides, one extending transversely of the arm and the other being formed at the forward surface of the arm. The two guides intersect each other and are disposed substantially in the same horizontal plane. A pair of thread tensioning discs are located in close proximity to the point of intersection of the two guides and the cooperating surfaces of the discs are disposed substantially coplanar with the guides. A manually adjustable dial associated with the tensioning means for adjusting the thread tension projects through a window opening in the forward surface of the arm. The thread is held securely between the tension discs against inadvertent displacement.

United States Patent [191 Kohara et al. Feb. 4, 1975 [54] THREAD TENSIONING DEVICE FOR 3,557,731 1/1971 Casas-Robert H 112/254 SEWING MACHINES FOREIGN PATENTS OR APPLICATIONS Inventors: Tadao Kohara; Iwao Takahashi. 458.036 8/1968 Switzerland 1 12/254 both of Osaka, Japan [73] Assignee: Maruzen Sewing Machine Co., Ltd., Primary Examiner-George Kflzmanich Osaka, Japan Attorney, Agent, or F1rmArnste1n,Gluck, Weitzenfeld & Minow [22] F1led: Sept. 4, 1973 [Zl] Appl. No.: 393,993 [57] ABSTRACT A sewing machine has an upper arm containing upper [30 Foreign Application priority Data thread tensioning means within the arm so as to be Sept 13 1972 Japan 47 m72l4 substantially concealed from view. The arm has two Oct 1972 Japan 474190]? thread guides, one extending transversely of the arm 1972 M 474 [3] 14 and the other being formed at the forward surface of p the arm. The two guides intersect each other and are [52] U 5 Cl 112/255 disposed substantially in the same horizontal plane. A [51] 47/00 pair of thread tensioning discs are located in close [58] Fieid 246 24 proximity to the point of intersection of the two guides 5 and the cooperating surfaces of the discs are disposed substantially coplanar with the guides. A manually ad- [56] References Cited justable dial associated with the tensioning means for adjusting the thread tension projects through a win- UNITED STATES PATENTS dow opening in the forward surface of the arm, The

Elcock thread is held securely between the tension discs etterer v. 3,190,249 6/1965 Gegauf 112/254 agamst Inadvertent d'splacemem' 3,347,195 l0/l967 Gegauf ll2/254 5 Claims, 7 Drawing Figures PAIENIEDFEB 4191s SHEET 3 OF 5 PATENTEU 75 SHEET l 0F 5 PATENTED 4W5 3.863.581

sum snr 5 THREAD TENSIONING DEVICE FOR SEWING MACHINES This invention relates to means for tensioning the upper thread in a sewing machine.

DESCRIPTION OF THE PRIOR ART Conventionally. the tensioning mechanism for the upper thread in a sewing machine comprised an assembly of a pair of cooperating dished discs. a spring and screw means for adjusting the spring pressure on the discs. This assembly generally was positioned on the front side of the upper arm below the lowermost limit of travel of the takeup lever. Such mechanism protruded forwardly of the arm so as to interfere with the operators unrestricted view of the needle and the article being sewn, as well as rendering the threading operation relatively complicated.

In a more recent development, as shown in US Pat. No. 3,190,249. an upwardly opening transversely extending slot is provided in the upper arm of the machine and the thread tensioning mechanism is disposed in the plane of the slot so that the thread is caused to ride over the shaft supporting the tension discs. The wraparound contact of the thread with the shaft is minimal because the thread is only slightly deflected from a straight line condition. Accordingly, under such conditions the effective engagement of the discs with the thread is minimal with the result that tensioning of the thread lacks uniformity thereby affecting the quality of the sewing operation. Indeed, the thread even may be displaced from between the discs requiring an interruption of the sewing operation.

SUMMARY OF THE INVENTION One of the objects of this invention is the provision of upper thread tensioning means located in the arm of the machine so as to be substantially concealed from view and arranged so as to effect substantially a 90 degree wrap around over the shaft supporting the tension ing discs thereby, assuring positive control of thread tensioning and eliminating the possibility of thread displacement.

Another object of this invention is the provision of thread tensioning means including two thread guides intersecting substantially at a right angle with the thread tensioning discs located at the intersection of said guides.

A further object of this invention is the provision of novel means for effecting release of the pressure on the tensioning discs.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a sewing machine embodying the invention.

FIG. 2 is an end elevational view, on an enlarged scale, illustrating the upper thread tension control means and tension release means. in accordance with this invention.

FIG. 3 is a fragmentary side elevational view of the mechanism illustrated in FIG. 2.

FIG. 4 is a fragmentary top plan view of the mechanism illustrated in FIG. 2.

FIG. 5 is an end elevational view similar to FIG. 2 and illustrating a modified embodiment of this invention.

FIG. 6 is a front elevational view of the mechanism illustrated in FIG. 5, and

2 FIG. 7 is a plan view of the mechanism illustrated in FIGS. 5 and 6.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, the numeral I2 designates a cover extending over a portion of the upper arm II of the sewing machine. The cover is provided with a first thread guide I3 extending transversely of the arm. the guide being defined by parallel vertical walls 14 and I4 which are joined together at the bottom to form a generally U-shaped trough. A portion of the wall I4 is cut away, as at 15. to afford clearance for inserting the thread T between the tension discs 21 and 22. as hereinafter will be described. As seen clearly in FIGS. I and 3. a lower portion of the front wall of the cover 12 is cut away to provide a second thread guide 16 which intersects and communicates with the guide I3.

The numeral A designates generally the upper thread tension control assembly which is mounted on a bracket 17 inside the arm 11 in close proximity to the point of intersection of the guides I3 and 16. The control assembly A includes a hollow shaft I8 affixed on bracket 17. The shaft 18 is intermediately stepped and terminates in a lower threaded portion 19 which is slotted inwardly longitudinally from its end, as at 27. A tension control dial 20 is in threaded engagement with the threaded portion 19. The dial 20 projects through a window opening provided in the forward wall of the arm 11 and is accessible for manual manipulation. A pair of cooperating dished tension discs 21 and 22 are loosely supported on a reduced intermediate portion of a shaft I8. A pressure plate 24, shaped substantially as illustrated in cross section in FIG. 3, is loosely carried on the lower portion of the shaft 18 and is arranged normally to abut the lower tension disc 22. The plate 24 is provided with a central aperture bridged by a traverse bar 26 which is received in the slot 27. A spring 25 interposed between the plate 24 and the dial 20 normally urges the tension discs 21 and 22 into pressing engagement. It will be apparent that rotation of the dial 20 will effect an adjustment in the pressure of the spring 25 acting on the discs 21 and 22. As clearly seen in FIG. 3, the lead-in or mouth portion 23. between the discs 21 and 22, is disposed substantially in horizontal registration with the bottom of the first guide 13 and the second guide I6 and that the outwardly turned edges of the discs are substantially tangent to guide 13. A tension release pin 28 is slideably received in the bore of the shaft 18 and the lower end of the pin abuts the traverse bar 26 of the plate 24. When the pin 28 is depressed, as will be hereinafter explained, the plate 24 is moved out of contact with the tension disc 22 so that pressure between the discs 21 and 22 is released.

Referring to FIG. 2, the numeral 40 indicates a conventional presser bar to the lower end of which is connected a conventional pressure foot 41. A lever 42 pivoted, as at 43, is provided with an intermediate actuating portion 44 which is adapted to engage a lift bracket 45 affixed to the presser bar 40. Rocking of the lever 42 in a clockwise direction as viewed in FIG. 2. will effect engagement of the portion 44 with the bracket 45 to lift the presser bar 40 against the action of spring 46 to raise the presser foot 41 above the needle hole plate, not shown.

A shaft 47 is rotatably supported in the frame of the head I] in parallel relation to the axix of pivot 43 and has fixed to one end a crank 48 which is connected by means of a link 49 to the lever 42. It will be apparent that rocking of lever 42 to raise presser foot 41 will effect simultaneous rotation of shaft 47 in a counter clockwise direction, as viewed in FIG. 2. A cam 50 is fixed on the opposite end of shaft 47 and is secured thereto in a position of adjustment by a set screw SI. A lever 52 is pivoted to the frame of arm I] intermediately thereof and has its lower end in contact with the cam 50 and its upper end in contact with the tension release pin 28. When the cam 50 is caused to be rotated by manipulation of lever 42, the lever 52 is caused to be rocked in a clockwise direction, as viewed in FIG. 2, to depress the pin 28 thereby, releasing the pressure between the discs 2I and 22. It will be understood that by adjusting the position of the cam 50 on shaft 47 the degree of movement of the lever 52 may be adjusted.

The letter B indicates generally a tension check spring assembly which is located below the upper thread tension control A and between this control and takeup lever 53. The assembly includes a guide frame 54 fixed in the arm 11 and a torsion spring 56, the function of which is to maintain tension on the thread for a purpose well known in the art.

In preparation for a sewing operation, the upper thread T is drawn off a supply spool, not shown, carried on a conventional spindle mounted rearwardly of the arm I]. As seen in FIG. 4, the thread T is inserted in the guide I3 in the cover 12 and as the operator swings it to the left, as viewed in FIG. 4, to engage the thread in fixed guide 55, the thread T is caused to enter the mouth 23 and is received between the tension discs 21 and 22. In such condition the thread is wrapped around the shaft I8 for approximately 90 and is confined between tension discs 21 and 22. Accordingly, positive tension is applied to the thread and the likelihood of the thread becoming disengaged from the tension discs during the sewing operation is entirely precluded. As seen in FIG. 3, from the guide 55 the thread is drawn downwardly into engagement with the check spring 56 and then passed through the aperture in the thread takeup lever 53 and from there drawn downwardly and threaded through the sewing machine needle.

In order to adjust the tension of the upper thread. the tension control dial which is partially exposed at the front of the arm 1] is rotated to obtain a desired spring pressure on the tension discs 21 and 22.

In the modified embodiment illustrated in FIGS. 5, 6 and 7, the conventional parts of the machine identical in both embodiments are identified by identical numerals and, accordingly, will not again be described. However. the parts in the modified embodiment of this invention corresponding to the parts of the first described embodiment are identified by numerals which are increased by I00.

Referring to FIGS. 5, 6 and 7, the cover "2 is provided with a transverse upper thread guide 113 defined by walls 114 and 114', the wall 114 being cut away, as at 115, for clearance purposes. The forward wall of the arm 11 is cut away, as at I10, corresponding substantially to the cut out I6 of the first described embodiment. The cut out IIO constituting guide I16 and guide II3 communicate with each other.

The letter A indicates the upper thread tension control assembly which is mounted within the arm ll in close proximity to the point of intersection of guide I13 and guide 116. The assembly A includes a hollow shaft 118 fixed vertically in a bracket I]? mounted in the arm 11. The shaft I18 is threaded at its lower end, as at 119, and is provided with a transverse slot I27 extending from the lower end upwardly for a major portion of its length. A tension control dial 120 having a depending cylindrical portion and shaped substantially as illustrated in FIG. 6 is loosely supported on the shaft I18. The dial 120 partially projects through a window opening in the front wall of the arm II and is readily accessible for manipulation for adjustment purposes, as will be hereinafter explained. As seen in FIG. 6, the upper surface of the control dial 120 is in horizontal registration with the fixed guide 55 and in effect constitutes part of the second thread guide II6. The dial I20 is provided with an upwardly opening recess 120'. Carried on the shaft 118 are a pair of cooperating dished tension discs 121 and I22 which are arranged to engage in a horizontal plane substantially coincident with the top surface of the dial I20. The outwardly turned edges of the tension discs I2] and I22 are substantially tangent to the guide II3 and form a mouth 123, as illustrated in FIG. 6. A pressure plate 124 provided with a central aperture bridged by an integral traverse bar I26 is loosely carried on the shaft II8 with the bar 26 being received within the slot I27. The pressure plate 124 abuts the lower tension disc I22 and is urged by a spring I25 into contact therewith. The lower end of the spring I25 abuts a flanged control member I29 which is internally threaded for engagement with the threaded portion 119 of the shaft I18. The spring I25 and control member I29 are enclosed within the cylindrical body 130 and the flanged member I29 is provided with a notch in its periphery to engage with a vertical projection I24 provided within the cylindrical body 130. Thus. the control member 129 and con trol dial 120 may be rotated as a unit with only the control member moving axially of the shaft I18 within the body 130 to adjust the pressure of the spring 125. A retaining washer I3] is provided on the lower end of the shaft II8 and is secured thereto as with a suitable screw. A pin I28 is slideably received in the bore of the shaft Il8 with its lower end engaging the traverse bar I26 of the pressure plate 124. When the lever 52 is actuated by elevation of the lever 42, the pin I28 acts on the pressure plate 124 thereby relieving pressure between the tension discs 12] and 122 so that the thread passing between the discs may be freely drawn therethrough.

Referring to FIGS. 6 and 7, it will be apparent that threading of the thread T through the machine is substantially identical with the procedure as described in the first embodiment.

It will be apparent from the foregoing description that a major portion of the tension control means is contained within the sewing machine arm and concealed from view with only a part of the control dial being exposed for adjustment purposes. Additionally, the first and second thread guides are arranged substantially at a right angle to each other, the tension discs being located in close proximity to the point of intersection of these guides with the cooperating surfaces of the discs being disposed substantially coplanar with the guides so that when the thread is received between the tension discs it is wrapped around the post supporting the tension discs for approximately 90 degrees thereby, insuring positive tension on the thread and minimizing the likelihood of the thread being inadvertently displaced from between the tension discs during a sewing operation.

Various changes coming within the spirit of our invention may suggest themselves to those skilled in the art; hence, we do not wish to be limited to the specific embodiments shown and described or uses mentioned, but intend the same to be merely exemplary, the scope of our invention being limited only by the appended claims.

We claim:

1. In a sewing machine including a vertical standard supporting a substantially horizontal upper arm having an upper surface and depending side and end surfaces, an upwardly opening first thread guide extending transversely of the upper surface of the arm fully between said side surfaces. a second thread guide formed at a forward side surface of said arm and intersecting and communicating with said first thread guide, a pair of cooperating spring biased thread tensioning discs contained below said upper surface and wholly within said arm and located in close proxto the point of intersection of said first and second guides, the thread engaging surfaces of said discs being substantially coplanar and disposed substantially in a horizontal plane with said first and second guides, and tension adjusting means operatively associated with said discs and including a manually adjustable dial co-axially operatively associated with said tension adjusting means and partially projecting outwardly of a window in the forward side surface of said arm.

2. The invention as defined in claim 1 including tension release means operatively associated with said discs.

3. The invention as defined in claim I in which the upper arm includes a cover forming its upper surface with said first and second thread guides being formed in said cover.

4. In a sewing machine including a vertical standard supporting a substantially horizontal upper arm having an upper surface and depending side and end surfaces, a vertically reciprocable presser bar, manual means for moving said presser bar upwardly, an upwardly opening first thread guide extending transversely of the upper surface of the arm fully between said side surfaces, a second thread guide formed at a forward side surface of said arm and intersecting and comcunicating with said first thread guide, a pair of cooperating spring biased thread tensioning discs contained below said upper surface and wholly within said arm and located in close proximity to the point of intersection of said first and second guides, the thread engaging surfaces of said discs being substantially co-planar and disposed substantially in a horizontal plane with said first and second guides, tension adjusting means operatively associated with said discs and including a manually adjustable dial co-axially operatively associated with said tension adjusting means and partially extending outwardly of a window in the forward side surface of said arm, and tension release means operatively associated with said discs and said presser bar and operative to release the tension of said discs when the presser bar is moved to its upward position.

5. The invention as defined in claim 4 in which the tension release means includes a pin operatively associated with said discs and an intermediately pivoted lever having one end engagable with said pin, a rotatable cam engagable with the opposite end of said lever, a crank connected to said cam and a lever connected to said crank and said manual means.

i l 1K i 3 

1. In a sewing machine including a vertical standard supporting a substantially horizontal upper arm having an upper surface and depending side and end surfaces, an upwardly opening first thread guide extending transversely of the upper surface of the arm fully between said side surfaces, a second thread guide formed at a forward side surface of said arm and intersecting and communicating with said first thread guide, a pair of cooperating spring biased thread tensioNing discs contained below said upper surface and wholly within said arm and located in close proxto the point of intersection of said first and second guides, the thread engaging surfaces of said discs being substantially coplanar and disposed substantially in a horizontal plane with said first and second guides, and tension adjusting means operatively associated with said discs and including a manually adjustable dial co-axially operatively associated with said tension adjusting means and partially projecting outwardly of a window in the forward side surface of said arm.
 2. The invention as defined in claim 1 including tension release means operatively associated with said discs.
 3. The invention as defined in claim 1 in which the upper arm includes a cover forming its upper surface with said first and second thread guides being formed in said cover.
 4. In a sewing machine including a vertical standard supporting a substantially horizontal upper arm having an upper surface and depending side and end surfaces, a vertically reciprocable presser bar, manual means for moving said presser bar upwardly, an upwardly opening first thread guide extending transversely of the upper surface of the arm fully between said side surfaces, a second thread guide formed at a forward side surface of said arm and intersecting and comcunicating with said first thread guide, a pair of cooperating spring biased thread tensioning discs contained below said upper surface and wholly within said arm and located in close proximity to the point of intersection of said first and second guides, the thread engaging surfaces of said discs being substantially co-planar and disposed substantially in a horizontal plane with said first and second guides, tension adjusting means operatively associated with said discs and including a manually adjustable dial co-axially operatively associated with said tension adjusting means and partially extending outwardly of a window in the forward side surface of said arm, and tension release means operatively associated with said discs and said presser bar and operative to release the tension of said discs when the presser bar is moved to its upward position.
 5. The invention as defined in claim 4 in which the tension release means includes a pin operatively associated with said discs and an intermediately pivoted lever having one end engagable with said pin, a rotatable cam engagable with the opposite end of said lever, a crank connected to said cam and a lever connected to said crank and said manual means. 